Scientific Journals
Zeszyty Naukowe
Maritime University of Szczecin
Akademia Morska w Szczecinie
2008, 13(85) pp. 40‐44 2008, 13(85) s. 40‐44
Analysis of the wind influence on the ship turning
manoeuvers on port turning basins
Analiza wpływu wiatru na manewr obracania statku
na obrotnicy portowej
Jakub Kornacki
Akademia Morska w Szczecinie, Instytut Inżynierii Ruchu Morskiego
70-500 Szczecin, ul. Wały Chrobrego 1–2, tel. 091 48 09 471, e-mail: kubi@am.szczecin.pl
Key words: ship manoeuvring, ship motion, ship hydrodynamics, ship aerodynamics, wind Abstract
The paper presents the problem of the wind influence on a ship during the turning manoeuvre and the influ-ence on this manoeuvre. Attention has been paid to the necessity of attaching larger attention to the influinflu-ence of the wind during the turning manoeuvre. The analysis of the wind influence on this manoeuvre has been conducted.
Słowa kluczowe: manewrowanie statkiem, ruch statku, hydrodynamika statku, aerodynamika statku, wiatr Abstrakt
W artykule został podjęty problem oddziaływania wiatru na statek podczas manewru obracania i wpływ na ten manewr. Zwrócono uwagę na konieczność przywiązywania większego znaczenia na oddziaływanie wiatru podczas manewru obracania. Przeprowadzono analizę wpływu wiatru na ten manewr.
Turning basins and the present state of art of their planning
Turning basins have two different meanings: the manoeuvring area appointed by the ships and also the hydro-technical building, artificial or natural, with suitable horizontal and vertical dimensions, where the considerable alterations of the course of the ship are executed. Obviously, the manoeuvre of the ship turning occurs very often in port manoeu-vres. It can be said that the ship turning is executed during every ship port call. The influence on the size of turning basin during the manoeuvre has many factors. Ship turnings are practices “in the place”. This should be understood as the change of the course of the ship whose linear speeds, during the manoeuvre, are close to zero. Turning the ship over is done on the turning basin as a result of the planned tactics of manoeuvring and can be done on itself or in co-operation with tugs or use of anchors
or spring. Turning basins are areas appointed and the reservoirs not appointed on which the turn of the ship is executed with the considerable value of the course and they are a part of channels or port basins. Certainly due to safety, the turning basin as the hydrotechnical building always has to be larger in all dimensions than the manoeuvre area to avoid the collision with bottom or bank [1].
While designing turning basins, two methods of defining their dimensions can be used. Those are analytic method and simulating method [2].
Analytic method is very simplified in that turn-ing basins are divided into two groups. The first group establishes non-current turning basins. The second group establishes turning basins on current waters. It is premised that the turn of the ship is described by the circular area, and in the case of current waters, the area is described by the shape similar to figures defined by two semicircle and two straight lines joining them – a stretched wheel
similar to an ellipse. The depth of water in turning basins is defined in dependence on loading status of the turned-over ships [2].
The dimension of the turning basin on the non-current waters is defined by the equation (1) [3, 4]:
OA
o L
d =1.5 (1)
The dimensions of turning basins on the current waters are defined by the equations (2), (3) [3, 4]:
o c OA o L v t l = 51. + (2) OA o L b =1.5 (3)
The simulating method of designing the parame-ters of turning basins is based on a series of tests in comparable conditions on a prepared model of reservoir and the model of the ship destined to use the turning basin. The results of tests are subject to the statistical processing. That kind of research results in delimitation of the area of manoeuvring on the turning basin according to the various foun-dations of hydrometeorological conditions, various parameters of ships and various levels of the trust. Characteristic feature of the simulating method is that simulating models of the ship manoeuvring are designed specially for the solved problem [5, 6, 7, 8].
Character of wind effect during full-scale trials
Investigations of the wind effect upon the ship manoeuvring have a long history. It does not mean that the previous studies have solved all the prob-lems. It is important to say that all application stud-ies of the wind effect in ship manoeuvring are very sensitive to the hydrodynamic mathematical model used. Most works refer to ship wind coefficients received as a result of scale model tests [9, 10].
The influence of very strong winds on manoeu-vring is serious. Of course, it depends on the ship type and the objectives of manoeuvring. In re-stricted water areas, ship manoeuvring remains under a speed of a few knots and the wind is not able to change the ship track and velocities so much. The situation can be worse in case of dy-namic positioning or low speed manoeuvring like ship turning.
Let us consider the case of a chemical tanker [11]. The ship data is summarised in table 1. Tests of ship turning are based on this model.
The ship outline is demonstrated in figure 1.
Fig. 1. The ship lateral windage area Rys. 1. Boczna powierzchnia nawiewu
The wind generalised forces (in terms of force and moment) are written as follows [9, 10]:
( )
( )
( )
= R mza L BP R fya L R fxa F R A zA yA xA c A L c A c A v M F F γ γ γ ρ 2 5 . 0 (4)The wind forces are a part of [9]:
+ + + = + + + = + + + = AzA AzR AzP AzH Az yA yR yP yH y xA xR xP xH x M M M M M F F F F F F F F F F (5)
The ship manoeuvring motion equations are as follows [9]:
(
)
(
)
(
)
(
)
(
)
(
)
= − + + = + + + = + − + Az y x z zz y z x y x z y x M v v m m t m J F v m m t v m m F v m m t v m m 11 22 66 11 22 22 11 d d d d d d ω ω ω (6)Analysis of wind effect during ships turning trials
The analysis of the wind effect during ship turn-ing on the turnturn-ing basin is based on the series of the ship turning tests. The tests have been executed in the wide port channel in various wind condition. Those tests apply the model of the ship mentioned above: chemical-tanker, with no tugboats, with its own propulsion, standard 35 degrees rudder and thrusters [11]. Port channel has the width of the quadruple of the length of the ship and has no in-fluence on the manoeuvring area. The tests have been carried out in the same places and interrupted after the ship’s turn-over to final course 270°.
First, just for the comparison, the series of tests has been conducted on three various models. Table 1. Full-scale ship data
Tabela 1. Dane statku
TYPE: chemical tanker
LOA 103.6 [m] H 9.4 [m]
LBP 97.4 [m] HA 35.2 [m]
BM 16.6 [m] AF 350 [m2]
A large crude tanker and a car-ferry have been taken beside chemical tanker for comparison. All these ships were in the same environmental condi-tion, that is: shallow water, slow speed, 5B wind, starboard turning and usage of ruder, main propul-sion (ahead/astern) and bow thruster, if available. Results have been shown in figures 2–5.
–50 0 50 100 –150 –100 –50 0 50 100 150 x Y [m] chem traincar crude
Fig. 3. Ships trajectories for starboard turning manoeuvre with different models
Rys. 3. Trajektorie statków dla manewru obracania różnych modeli
The drift is defined as an angle between ship heading and direction of speed over ground vector.
One can see in conducted tests that the ferry turned the most quickly, with the biggest turn rate in all range of courses and draught the smallest trajectory. Obviously, the reason for it was that the the ship was equipped with the best propulsion. The final position has been shifted in relation to the initial one above the width of the ship (around 25 m).
The slowest turning was made by the crude tanker because of the largest dimensions and only one main propulsion without thrusters. Of course, that kind of ships have a tug assistant in natural situation. It is interesting that the final position of the ship in relation to initial position has been shifted more or less the same (around 25 m). Obviously, the wind force according to displace-ment is much weaker.
chem traincar crude 0 5 10 15 20 25 30 35 ships type co mma nd s
Fig. 4. Comparison of commands quantity during turning manoeuvre
Rys. 4. Porównanie ilości wydanych komend podczas manew-ru obracania
The time of manoeuvres is similar, but the quan-tity of commands is completely different. Because of the large amount of steering elements on train-car-ferry, the most commands take place there.
The main test was the analysis of the wind effect during ship turning on the turning basin. The tests were executed in three different wind conditions, without wind, with north wind – 5B, and with south wind – 5B. The results of the tests have been shown below. –200 –150 –100 –50 0 50 100 150 200 0 50 100 150 200 250 300 course [o] dr if t [ o] chem traincar crude
Fig. 5. Drift direction according to ships courses for different models
Rys. 5. Wartość kąta dryfu w zależności od kursu statków dla różnych modeli
Figures 6–8 present manoeuvring areas, turning speed according to ships course and average time of manoeuvres divided in three groups. Very interest-ing is that all the three test groups have shown simi-lar final position offset compatible with wind direc-tion. It is possible to see similar turn rate offset as well.
Of course, the wind conditions are more difficult for manoeuvring thus it takes longer. Obviously, turning to starboard is easier and therefore trials with southern wind are shorter than trials with northern wind. –10 0 10 20 30 40 50 60 70 0 50 100 150 200 250 300 Course [o] turning s pe ed [o/m in] chem traincar crude
Fig. 2. Ship turning speed according to ships courses on dif-ferent models
Rys. 2. Prędkość kątowa w funkcji kursu dla różnych modeli statków
-150 -100 -50 0 50 100 150 -250 -200 -150 -100 -50 0 50 100 150 200 250 x [m] y [ m ] wind_O wind_5N wind_5S Pianc
Fig. 6. Manoeuvring area for ships turning – chemical vessel, series of 30 trials in different wind conditions
Rys. 6. Obszar manewrowy podczas obracania statku – chemi-kaliowiec, seria 30 prób w różnych warunkach wiatrowych
Lateral manoeuvring areas offsets are around 25 m to each side. Accepting the steady working of the wind in the steady direction, it can be:
= = s F W c A v F A A fa R A A 0.5ρ 2 (7)
Working of the wind can be understood as the kinetic energy causing position offset. Knowing above-water average area, the air density, the wind velocity, aerodynamic coefficients and work we can accept: fa A A d c A v mv s 2 2 ρ = (8)
where s means final position offset and m means total mass of the ship and non-current water. Of course it needs future examination.
Final remarks
Based on the above examinations, some general points can be formulated.
It is harder to execute the manoeuvre of the turn-ing at small speeds. What the time of the manoeu-vre lengthens, the growth of the wind influence causes. It is much better to approach faster than rapidly stop the ship and start fast turning into di-rection of wind impact.
While being in line of wind impact, it is neces-sary to remember about rapid acceleration in direc-tion of wind impact.
Obviously, the wind has influence on the posi-tion of manoeuvring area making offset, but it has no great influence on the size of the manoeuvring area. It is similar to the case of current influence but the effects are less significant. It suggests using offset parameter to define turning basin dimensions during windy conditions. The offset formula needs future tests.
Symbols
A – above-water average area [m2],
AF – above-water frontal area [m2],
AL – above-water lateral area [m2],
bo – width of the turning basin [m],
BM – moulded breadth [m],
cfxa, cfya, cmza – aerodynamic coefficients [–], [–], [–],
do – diameter of the turning basin [m],
Fx, Fy, MAz – external total surge, sway forces and yaw
mo-ment [N], [N], [Nm],
H – depth [m],
HA – air draught from the keel [m],
LBP – length between perpendiculars [m],
LOA – length over all [m],
lo – length of the turning basin [m],
m, Jzz – mass and inertia moment [kg], [kg m2],
m11, m22, m66 – virtual masses [kg], [kg], [kg m2],
S – final position offset [m],
TM – draught [m],
to – time of the turning [s],
vc – speed of the current [m/s],
vd – drifting speed [m/s],
vR – relative wind velocity [m/s],
-60 -40 -20 0 20 40 60 0 50 100 150 200 250 300 350 400 course [o] tu rn in g spee d [o /m in ] wind_5S wind_O wind_5N
Fig. 7. Turning speed acc. to ships course – port and starboard turning
Rys. 7. Prędkość kątowa w funkcji kursu – obrót na lewą i prawą burtę wind_O wind_5N wind_5S 390 400 410 420 430 440 450 460 470 trials ti m e [s ]
Fig. 8. Average time of manoeuvres in different wind condi-tions
Rys. 8. Średni czas trwania manewru w różnych warunkach wiatrowych
vx, vy, ωz – surge, sway and yaw velocity [m/s], [m/s], [1/s],
γR – relative wind direction [deg],
ρA – air density [kg/m3],
WA – work of wind [J],
H, P, R, A – subscripts indicating respectively: hull,
propel-ler, rudder or wind.
References
1. KORNACKI J., GALOR W.: Analysis of ships turn manoeu-vres in port water area. TransNav’07, Gdynia 2007. 2. KORNACKI J.: The analysis of the methods of ship’s
turn-ing-basins designing. XII International Scientific and Technical Conference on Marin Traffic Engineering, Mari-time University of Szczecin, 2007.
3. GUCMA S., JAGNISZCZAK I.: Nawigacja dla kapitanów. Fundacja Promocji Przemysłu Okrętowego i Gospodarki Morskiej, Gdańsk 2006.
4. MCCARTNEY B.: Ship Channel Design and Operation.
American Society of Civil Engineers, 2005, 107.
5. The unpublished report. Badania symulacyjne ruchu stat-ków w bazie paliw płynnych w Świnoujściu. Maritime University of Szczecin, 1995.
6. The unpublished report. Określenie optymalnego wariantu przebudowy wejścia do portu Kołobrzeg w oparciu o bada-nia symulacyjnego ruchu statków. Maritime University of Szczecin, 1995.
7. The unpublished report. Badanie możliwości optymalnej lokalizacji przeładowni kwasu fosforowego w Porcie Poli-ce. Maritime University of Szczecin, 1998.
8. The unpublished report. Analiza nawigacyjna dla przebu-dowanego Nabrzeża Górników w porcie handlowym Świ-noujście. Maritime University of Szczecin, 2000.
9. ARTYSZUK J.: Wind Effect in Ship Manoeuvring Motion
MM – a Review Analysis. International Scientific-Technical Conference Explo-Ship 2002, Maritime Univer-sity of Szczecin, 2002.
10. ARTYSZUK J.: Sensitivity of Ship Manoeuvring Trials upon
Wind and Irregular Wave Action. Szczecin/Kopenhagen, Scientific Bulletin, Maritime University of Szczecin, 2004, 65.
11. ARTYSZUK J.: Methodical guide of the ships manoeuvring
simulation with application. Maritime University of Szczecin, 2005.
Recommended literature
1. BRIX J.: Manoeuvring Technical Manual. Seehafen Verlag, Hamburg 1993.
2. GUZIEWICZ J., ŚLĄCZKA W.: The methods of assigning
ship's manoeuvring area applied in simulation research. In-ternational Scientific and Technical Conference on Sea Traffic Engineering, Szczecin 1997.
Recenzent: dr hab. inż. Lucjan Gucma, prof. AM Akademia Morska w Szczecinie
